That's likely a part of it, FTB. I've never seen a calibration sticker on a mod
After about 22 years in the electronics industry, and knowing approximately the knowledge base of the current major mod manufacturers, the on-board VOMs "could" be accurate to a hundredth of a volt with no significant increase in cost per unit. Did that make sense? That is, the retail price of the SXmini is $199 and you can get that kind of accuracy in a stand-alone VOM for about $5, so there is no reason whatsoever why this mod should not be accurate. I'm
not saying it
is accurate - as you say, they do not certify calibration, but it damn well should be.
The type of regulation circuit can make a difference as well - i.e. how smooth a DC voltage is actually output. And, as Robert mentioned, some just can't fire below the battery voltage, no matter what you set. Those generally perform better at the high end of their range - which doesn't do me much good, as I'm usually between about 7 - 9 watts!
OK, check me out on this simple math (I know you can...): The on-board VOM claims the coil resistance is 1.85 Ohms. The current actual battery voltage is 3.72 Volts (I have already consumed 13,578.2 Joules from full charge). When I set the Wattage at 18.0, the chip calculates that it will require 5.75 Volts to achieve that heat level. Good old Ohm's Law says E=IR and P=IE, therefore P=EE/R, therefore E=Sq.rt. of (PR), so the square root of (18.0x1.85) = 5.77 Volts which puts the on-board calculator off by only 0.02 Volts that the regulator circuitry would have to bump the output up to in order to achieve 18.0 Watts. Of course, any inaccuracy by the on-board VOM in measuring the coil resistance or the available voltage versus calculated voltage requirement would introduce sufficient error to accommodate that 0.02 Volt issue (or more). Given the iStick TC40 that I compared this to is a $40 mod, I would tend to place the reading/calculation error on that side rather than the SXmini. Which one of those guys has the better reputation for accuracy? Or is the answer "neither"?
On the one hand I find it highly unlikely that the chips are that accurate. On the other hand one could assume that the chips in identical mods would be pretty close to the same.
I agree, Gary, that the chips in the same model of mods should be identical (assuming little-to-no manufacturing tolerance errors) and chips from different manufacturers are very likely to not agree with each other, but as I implied above, the technology and the potential for accuracy
is available and the cost differential should be next to nothing. So, am I being an idiot to assume these people would
want to build the best possible instruments, or is this just another version of "let's con those stupid Americans because they'll buy any piece of crap as long as it looks impressive"?
